Mitigating arsenic contamination and boosting rice yield with natural and anthropogenic H2O2 sources

Mitigating arsenic (As) accumulation in rice while maintaining yield is a critical challenge for food safety. This study demonstrates that in-situ reactive oxygen species (ROS) generation, driven by hydrogen peroxide (H 2 O 2 ) from natural rain and anthropogenic source (urea hydrogen peroxide, UHP), effectively addresses this challenge. A pot experiment revealed that both H 2 O 2 sources, especially UHP, significantly induced in-situ production of ROS levels (H 2 O 2 and hydroxyl radicals (•OH). The ROS burst effectively suppressed the mobility of As by oxidizing 57-83% of the mobile As(III) to the less bioavailable As(V) in soil porewater during the heading stage, thereby significantly reduced As accumulation in both aboveground and belowground tissues by 15.3-34.7%. Critically, total As concentration in rice grains was markedly decreased by 17.7-30.1% under both H 2 O 2 sources, with UHP being more effective than rain, and showed significant negative correlations with both H 2 O 2 and •OH levels. Simultaneously, rice yield was significantly improved, showing the greatest enhancement under UHP amendment, and demonstrating a strong positive correlation with ROS levels. These findings confirm that H 2 O 2 -driven ROS generation, particularly from UHP amendment, provides a promising in-situ strategy for the dual goals of reducing grain As accumulation and enhancing yield in As-contaminated paddy fields. • Rainwater-borne H 2 O 2 triggered hydroxyl radical ( ● OH) production in paddy soils • Application of urea hydrogen peroxide (UHP) also generated in-soil ● OH • UHP application resulted in stronger in-soil ROS generation compared to rain • Elevated ● OH levels concurrently enhanced rice yield and reduced grain-As • Findings have implications for managing As contamination in paddy rice systems